Fix "unreachable code" warnings (MSVC warning 4702) in ui/.

ui/shell_dialogs/select_file_dialog.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/shell_dialogs/select_file_dialog.h"
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
 #include "build/build_config.h"
@@ skipping 76 matching lines @@
 #if defined(OS_WIN)
   // TODO(ananta)
   // Fix this for Chrome ASH on Windows.
   return CreateWinSelectFileDialog(listener, policy);
 #elif defined(OS_MACOSX) && !defined(USE_AURA)
   return CreateMacSelectFileDialog(listener, policy);
 #elif defined(TOOLKIT_GTK)
   return CreateLinuxSelectFileDialog(listener, policy);
 #elif defined(OS_ANDROID)
   return CreateAndroidSelectFileDialog(listener, policy);
+#else
+  return NULL;
 #endif
-
-  return NULL;
 }
 
 void SelectFileDialog::SelectFile(
     Type type,
     const base::string16& title,
     const base::FilePath& default_path,
     const FileTypeInfo* file_types,
     int file_type_index,
     const base::FilePath::StringType& default_extension,
     gfx::NativeWindow owning_window,
@@ skipping 39 matching lines @@
 void SelectFileDialog::CancelFileSelection(void* params) {
   if (listener_)
     listener_->FileSelectionCanceled(params);
 }
 
 ShellDialogsDelegate* SelectFileDialog::GetShellDialogsDelegate() {
   return g_shell_dialogs_delegate_;
 }
 
 }  // namespace ui